2IO 



LEAVES 



The arrangement of leaves is described by the terms 

 alternate, opposite, and whorled. Alternate leaves are one 

 at a node; they appear to alternate, first on one side of 

 the stem, then on a different side. (See Figure 69.) Op- 

 posite leaves are two at a node. (See Figures 72 and 73.) 



Fig. 73. — A horizontal twig of Norway maple having opposite leaves. Note also 

 the differences in the lengths of the petioles whereby the shading of one leaf by 

 another is avoided. 



Whorled leaves are more than two at a node. The parts of 

 a flower are usually arranged in whorls. 



If you examine a stem with alternate leaves, you find 

 that an imaginary line drawn through the points of attach- 

 ment of the leaves forms a spiral around the stem. The 

 advantage of this arrangement is evident. It avoids 

 shading. (See Figure 74.) Even more striking in getting 

 this result is the arrangement of opposite leaves. Often 

 in the woods, or in greenhouses, you may find young plants 



